JP2002349422A - Radial piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent applying of falling moment not preferable to a piston, in the piston generating a protruding/sinking stroke of the piston by pressing the piston arranged in a radial direction by an eccentric cam. SOLUTION: By forming an external peripheral shape of the eccentric cam 33 from a cylindrical shape to a polygonal shape, and by changing a shape in the top end 23 of the piston 21 from a plane to a spherical shape, an acting point when the eccentric cam 33 presses up the piston 21 is always conformed to a piston center axis m, and a problem of generating of falling moment is solved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to various hydraulic equipment,
The present invention relates to a radial piston pump suitably applied to industrial equipment.

[0002]

2. Description of the Related Art FIGS. 4 and 5 show a conventional example of such a radial piston pump. To explain the configuration based on the function as a pump, radial bores 1 formed at an inner circumferential equiangular position of the housing H and these bores 1
A piston 2 having a suction hole 21 on a side surface and having a suction end 21 formed flat and having a flat tip 22 is disposed at an inner peripheral position of the housing H so that the distal end 22 of the piston 2 can simultaneously contact the outer peripheral surface. And an eccentric cam 3. The piston 2 has its proximal end elastically urged by a spring 24, and maintains a state in which the distal end 22 is always in contact with the eccentric cam 3.

The eccentric cam 3 is, specifically, a cylindrical cam body 31 integrally formed at an eccentric position of a rotary shaft 34, and a cylindrical body rotatably fitted to the outer periphery of the cam body 31. When the rotating shaft 34 integrated with the cam body 31 rotates, the piston 2 is caused to protrude and retract through the cam ring 32.

[0006] With the retraction of the piston 2, as shown by an arrow in FIG. 5, the hydraulic fluid entering from the suction port 4 is discharged from the suction hole 2 on the side surface of the piston at the bottom dead center of the piston 2.
1, the suction hole 21 is closed and pushed out by the bore 1 when the piston 2 rises. A reed valve 6 is provided at the outlet of the passage. The reed valve 6 allows the hydraulic fluid to pass therethrough in the discharge process and causes the hydraulic fluid to flow out from the discharge port 7. However, in the suction process after the piston 2 has passed through the top dead center, the reversing valve closes the passage. Functions as a stop valve. When the piston 2 reaches the bottom dead center by being pushed by the spring 24, the hydraulic fluid flows again through the suction hole 21 on the side surface of the piston 2, and the above process is repeated.

[0005]

However, in such a configuration, when the cam ring 32 pushes up the piston 2, the point of action does not coincide with the center axis of the piston 2, and a tilting moment is generated with respect to the piston 2. . This is shown in FIG.
Explaining based on (a), when the rotating shaft 34 rotates and the piston 2 moves up and down to repeat the discharging process and the sucking process, the contact between the tip 22 of the piston 2 and the cam ring 32 moves with respect to the central axis m of the piston 2. Therefore, when the piston 2 is pushed up by the cam ring 32, the piston 2 is tilted to generate a moment. Then, this falling moment must be supported on the side surface of the piston 2 while sliding between the piston 2 and the bore 1, and it is necessary to ensure a relatively large length of the piston 2 and the bore 1 (total diameter ratio). However, there has been a certain limit to miniaturization of the entire pump. In addition, the sliding caused by the falling moment results in a loss torque, which is a factor of reducing the mechanical efficiency of the pump.

[0006]

In order to solve the above-mentioned problems, the present invention is directed to an eccentric cam in which the outer peripheral shape is changed from a cylindrical shape to a polygonal shape, and the tip shape of the piston is changed from a flat to a spherical shape. It is.

Thus, the point of action when the eccentric cam pushes up the piston always coincides with the center axis of the piston. Then, when the line of action of the force by which the eccentric cam pushes up the piston coincides with the center axis of the piston, the piston can be stroked without generating a falling moment.

The specific structure of the eccentric cam for that purpose can be realized by fitting a polygonal cam ring to the outer periphery of a cam body integrally formed at the eccentric position of the rotating shaft. At this time, since the rotation center of the polygon cam ring and the reaction force of the force pushing up the piston are shifted, the polygon cam ring is not synchronized with the piston. Therefore, it is preferable to adopt a synchronization mechanism for maintaining the posture of the polygon cam ring. As an example of the synchronization mechanism, a timing pin integrally projecting from the polygon cam ring in a direction parallel to the axis and a timing ring which is stationary and regulates an operation area of the timing pin at an inner peripheral position are provided. Are performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In addition, this embodiment will also describe the configuration based on the function as a pump, and portions common to FIG.
Description is omitted.

The radial piston pump of this embodiment has a structure in which the outer peripheral surface of the eccentric cam 3 interlocked with the reciprocating motion of the piston 2 is made polygonal, the tip 23 of the piston is made spherical, and no tilting moment is generated on the piston 2. It is what it was.

Specifically, the eccentric cam 3 includes a cylindrical cam body 31 provided eccentrically from the rotation shaft 34 and integrally provided with the eccentric cam 3.
A polygonal cam ring 33 is fitted to the outer periphery of the cam body 31 so as to be relatively rotatable. In this embodiment, since the number of pistons 2 is eight, the polygonal cam ring 33 is an octagonal ring. It has been.

On the other hand, the piston 2 has a tip 23 formed in a partially spherical shape, and is set so that the top is located on the central axis m.

The pistons 2 are accommodated so as to be able to protrude and retract in bores 1 provided at eight locations on the circumference in the radial direction, and each tip 23 is provided on the outer peripheral surface of the polygonal cam ring 33, ie, each piston 2 Of the polygonal cam ring 33 oppose each other.

Further, in order to maintain the posture of the polygonal cam ring 33 with respect to the piston 2 and to keep the flat surface of the polygonal cam ring 33 and the center axis m of the piston 2 orthogonal at all times, the synchronization shown in FIG. The mechanism S is configured. The synchronous mechanism S integrally projects a plurality of (four in the case of this embodiment) timing pins 8 integrally with each other in a direction parallel to the rotation shaft 34 from an equiangular position of an end face of the polygonal cam ring 33. The plurality of (four in this embodiment) timing rings 9 are supported by the housing H and can restrict the operation area of the timing pins 8 at the inner peripheral position.
Is provided.

When the rotating shaft 34 rotates, the timing pins 8 are brought into sliding contact with the inner periphery of the corresponding timing ring 9 while maintaining the posture of the polygonal cam ring 33 at a plurality of locations (four locations). , Enables a pivoting operation around the rotation axis 34.

Therefore, when each piston 2 performs the protruding / retracting operation by the polygonal cam ring 33, the contact point of the piston tip 23 with the flat surface of the cam ring slides in the surface direction, but when the flat surface pushes up the piston 2, The point of action is always the piston 2 as shown in FIG.
It will coincide with the central axis. For this reason, the piston 2 can be stroked without generating a falling moment, so that the loss torque can be reduced and the entire length of the piston 2 can be shortened.

The specific configuration of each section is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0018]

Since the present invention has the above-described structure, the following effects can be obtained.

First, conventionally, a relatively large overall length and diameter ratio were required for the piston in order to receive a load on the side surface of the piston due to the falling moment. However, according to the present invention, the overall length of the piston can be shortened. It is possible to effectively reduce the size.

Further, in the prior art, since a falling moment acts on the piston, the sliding resistance between the piston and the bore is a loss torque. However, according to the present invention, the loss torque can be reduced because the piston does not generate a falling moment. Thus, it is possible to effectively improve the mechanical efficiency of the pump.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention.

FIG. 2 is a principle diagram for explaining the operation of FIG. 1 in comparison with a conventional problem.

FIG. 3 is an exemplary view for explaining main parts of the embodiment.

FIG. 4 is an overall vertical sectional view showing a conventional example.

FIG. 5 is a cross-sectional view of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bore 2 ... Piston 3 ... Eccentric cam 8 ... Timing pin 9 ... Timing ring 21 ... Suction hole 23 ... Partially spherical piston tip 24 ... Spring 31 ... Cam main body 32 ... Cylindrical cam ring 33 ... Polygon cam ring 34 ... Rotation Shaft H: Housing S: Synchronous mechanism

Claims (1)

[Claims] 1. A radial bore formed at an equiangular position on an inner circumference of a housing, a piston housed in these bores so as to be able to protrude and retract and having a suction hole on a side surface, and a tip of the piston contacting an outer circumferential surface at the same time. An eccentric cam arranged at the inner peripheral position of the housing to interlock the rotation of the eccentric cam with the reciprocation of the piston in the radial direction, and to connect the suction hole to the suction port at the bottom dead center of the cam to bore the bore. In a configuration in which the hydraulic fluid flows into the bore and the hydraulic fluid in the bore flows out through a passage provided with a check valve before reaching the top dead center of the cam, thereby performing a function as a pump, The radiator is characterized in that the eccentric cam linked to the reciprocating motion of the piston has a polygonal outer surface, and the piston tip has a spherical shape so that the piston does not fall down and generate a moment. Piston pump.